Hi Marc,
Having looked I see that I could easily use the date passed in but I am concerned this may not work well. We store dates as UTC and we adjust it to user local time in the web ui based on profile setting for timezone offset and if not authenticated based on preferred GMT offset in Web.config.
I "think" WLW passes in the date already converted to UTC and if that is correct it should work fine because we store dates that way already. If I'm wrong it could cause things to be published at the incorrect time.
What I will do is wrap a Web.config setting around it so if it does cause any problems using the passed in date it can be disabled easily in config to go back to the previous behavior of using the server current time. This will be in the next release.
Best,
Joe